1
1 mark
1 markWhich component of blood has a role in preventing pathogens from entering the body?
Red blood cells
Blood plasma
Platelets
White blood cells
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Syllabus Edition
First teaching 2014
Last exams 2024
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6.3 Defence Against Infectious Disease
21 mark
1 markWhat is the principle purpose of sebum secretions onto the surface of the skin?
To prevent microorganisms from sticking to the skin.
To lower skin pH, which slows down the growth rate of microorganisms.
To provide a surface texture to the skin that aids the evaporation of sweat.
To assist in the formation of blood clots as a way of sealing wounds after a cut or graze.
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31 mark
1 markThis question is about the proteins involved in blood clotting.
Which shows the 3 boxes on the left joined to the appropriate one on the right?
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41 mark
1 markWhich phrase best fits into the gap in the following sentence?
| The shape of antibody molecules gives each one a particular 3-D configuration. This allows each antibody to be ______________ each individual pathogen. |
...well suited to...
...specific to...
...functional against...
...the same shape as...
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51 mark
1 markWhich pair of scientists carried out research work that built upon the discovery of antibiotics by Alexander Fleming in 1929?
Darwin and Wallace
Crick and Watson
Meselson and Stahl
Florey and Chain
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11 mark
1 markRoutine use of antibiotics in animal feed has been common practice in livestock farming, but is now no longer widely practised.
Which statements best explain why?
- Use of antibiotics allows sub-standard hygiene conditions for farm animals to be kept in
- It encourages antibiotic resistance
- It is expensive
- Farm animals get more nutrition from antibiotic-free feed
II. and III.
I. and II.
I. II. and III.
All of them
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21 mark
1 markThe image below shows a petri dish viewed from above. A lawn of bacteria is growing across the whole surface of the agar.
Different antibiotics, X and Y were applied to the agar before inoculating it with bacteria. Both antibiotics were applied to the discs of filter paper at the same concentration.
The plates were then incubated for 24 hours at 25°C. Zones of inhibition (areas of the dish with no bacterial growth) are shown on the diagram. 
After growth, the following results were obtained.
| Antibiotic | Diameter of zone of inhibition / cm |
| X | 2.0 |
| Y | 6.0 |
How many times more effective was antibiotic Y versus antibiotic X in this study?
3×
9×
12×
18×
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31 mark
1 markWhich is a reason why fungi such as Penicillium have evolved to produce antibiotics?
To destroy bacteria that could otherwise feed on Penicillium
To destroy bacteria that could otherwise harm the fungus's host organisms
To destroy saprophytic bacteria as a way of Penicillium out-competing bacterial competitors for food
To kill viruses that may otherwise be pathogenic to the fungus
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41 mark
1 markSome bacteria develop resistance to antibiotics by forming biofilms, which are large colonies of bacteria clumped together.
Which statement best explains how forming a biofilm might give a bacterial species resistance to antibiotics?
Antibiotic molecules are physically unable to reach all bacterial cells in a biofilm
Biofilms secrete chemicals which break down the antibiotic
Biofilms remain in a host organism for many years
Bacterial cells in a biofilm go into a suspended state but can become infectious again at a later stage
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51 mark
1 markLefamulin™ is a newly-developed antibiotic that binds to the 50S bacterial ribosomal subunit.
It was approved by the US Food and Drug Administration (FDA) in August 2019 for the treatment of pneumonia.
Which is the mode of action of Lefamulin™?
Inhibits bacterial protein synthesis
Perforates the bacterial cell membrane
Prevents the bacterial cell wall forming
Inhibits replication of bacterial DNA
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11 mark
Which of the following are considered primary defence against infectious disease?
Skin and mucous membranes.
Hair and skin.
Phagocytes and fever.
Lymphocyte production of antibodies.
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21 mark
Avian bird flu is caused by the H5N1 virus. Scientists are concerned that this could affect humans and cause a pandemic.
Which of these measures would help prevent the spread of disease in humans?
Reducing the number of flights between different countries.
Killing all birds.
Taking a course of antibiotics.
Increasing the number of winter flu vaccines administered.
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31 mark
Bacteria and viruses are the main pathogens in humans. Antibiotics can be used to treat bacterial infections but not viral infections.
Which of the following statements explains why?
Viruses need a host to survive.
Viruses consist of just nucleic acid and a protein coat.
Bacteria have peptidoglycan cell walls.
Viruses are significantly smaller than bacteria.
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41 mark
An antibiotic sensitivity test was performed on bacteria isolated from a patient’s throat.
The diagram shows the results of the four antibiotics tested.
Which one should be used to treat the disease?
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51 mark
When a phagocyte responds to the presence of a pathogen the following events happen:
- Enzymatic digestion.
- Endocytosis.
- Phagocyte membrane extends out.
- Vacuole formation.
Which of the following would be the correct order of events?
|
|
first |
→ |
→ |
last |
|
A |
III |
I |
IV |
II |
|
B |
III |
II |
IV |
I |
|
C |
II |
IV |
I |
III |
|
D |
II |
III |
IV |
I |
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61 mark
Which of these statements correctly describes a lymphocyte?
They have many mitochondria to produce ATP to allow endocytosis of pathogens.
They have many lysosomes containing hydrolytic enzymes to digest pathogens.
They provide specific defence against disease-causing organisms.
They are white blood cells with a lobed nucleus.
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71 mark
The diagram represents the process of blood clot formation.
What is the correct sequence of events
| I | II | III | IV | |
| A | Prothrombin | Thrombin | Fibrin | Fibrinogen |
| B | Clotting factors | Thrombin | Fibrinogen | Fibrin |
| C | Fibrin | Fibrinogen | Thrombin | Clotting factors |
| D | Clotting factors | Thrombin | Fibrin | Fibrinogen |
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81 mark
What is specific immunity?
Treating a specific disease through use of antibiotics.
Production of monoclonal antibodies.
Production of antibodies by lymphocytes.
Endocytosis of pathogens by phagocytes.
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91 mark
Which of the following is not a contributing factor towards the development of antibiotic resistance in bacteria?
Stopping a course of antibiotics once symptoms improve.
Development of new antibiotics.
Natural selection which favours mutations in bacteria.
Overuse of antibiotics in agriculture
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101 mark
The following statements are about people infected with HIV/AIDS.
- They will have symptoms.
- They can be treated and completely cured.
- They may live for many years after infection.
Which ones are correct?
I only
I and II
I and III
III only
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